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Lesson 12 - StreamAPI in Java - Modifying stream methods

In the previous lesson, StreamAPI in Java - Generating streams, we looked at ways to create general and numeric streams. In today's Java tutorial, we're going to learn about another methods, that modify streams.

Stream modification methods

Modification methods apply some rules to an existing stream and create a new one.

The filter() Method

The method's signature is as follows:

filter(Predicate<? super T> predicate)

As the name suggests, the method creates a new stream of elements that match specified criteria. Let's show the usage on an example:

    .of("Peter", "Michael", "Carl", "John", "Martin", "Jack")
    .filter(name -> name.startsWith("J"))

The result is all the names starting with the letter "J":

Console application

The distinct() Method

Let's start with the method signature again:


The method creates a stream of unique values from the original stream. To achieve the uniqueness, the values are compared internally using the


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In this Java tutorial, we'll learn about StreamAPI methods that modify existing streams and create new ones.

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Article has been written for you by Petr Štechmüller